Document Type

Article

Journal Title

PLoS One

Publication Date

Fall 10-16-2015

Volume

10

Abstract

The human CLCA4 (chloride channel regulator, calcium-activated) modulates the intestinal phenotype of cystic fibrosis (CF) patients via an as yet unknown pathway. With the generation of new porcine CF models, species-specific differences between human modifiers of CF and their porcine orthologs are considered critical for the translation of experimental data. Specifically, the porcine ortholog to the human CF modulator gene CLCA4 has recently been shown to be duplicated into two separate genes, CLCA4a and CLCA4b. Here, we characterize the duplication product, CLCA4b, in terms of its genomic structure, tissue and cellular expression patterns as well as its in vitro electrophysiological properties. The CLCA4b gene is a pig-specific duplication product of the CLCA4 ancestor and its protein is exclusively expressed in small and large intestinal crypt epithelial cells, a niche specifically occupied by no other porcine CLCA family member. Surprisingly, a unique deleterious mutation of the CLCA4b gene is spread among modern and ancient breeds in the pig population, but this mutation did not result in an apparent phenotype in homozygously affected animals. Electrophysiologically, neither the products of the wild type nor of the mutated CLCA4b genes were able to evoke a calcium-activated anion conductance, a consensus feature of other CLCA proteins. The apparently pig-specific duplication of the CLCA4 gene with unique expression of the CLCA4b protein variant in intestinal crypt epithelial cells where the porcine CFTR is also present raises the question of whether it may modulate the porcine CF phenotype. Moreover, the naturally occurring null variant of CLCA4b will be valuable for the understanding of CLCA protein function and their relevance in modulating the CF phenotype.

MeSH Headings

Amino Acid Sequence, Animals, Base Sequence, Chloride Channels, Cystic Fibrosis, Cystic Fibrosis Transmembrane Conductance Regulator, Electrophysiology, Epithelial Cells, Humans, Intestines, Male, Molecular Sequence Data, Mutation, Phenotype, RNA, Messenger, Rabbits, Real-Time Polymerase Chain Reaction, Reverse Transcriptase Polymerase Chain Reaction, Sequence Deletion, Sequence Homology, Amino Acid, Sequence Homology, Nucleic Acid, Species Specificity, Swine

ISSN

1932-6203

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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